Holoprosencephaly--report of two cases.

Holoprosencephaly (HPE) is a developmental defect resulting from incomplete cleavage of the embryonic forebrain structures during early embryogenesis. It includes a series of rare complex disorders. Chromosomal abnormalities, single gene disorders and teratogenic agents are responsible for holoprosencephaly. We report two rare cases of alobar HPE with a rudimental nasal structure (proboscis) located under the eyes. One of the patients survived for 9 months and the other one survived 40 days.